A power conversion apparatus and a controlling method thereof are disclosed. The power conversion apparatus is applied with a power generation apparatus, which outputs a first signal. The power conversion apparatus includes a conversion-sensing circuit, a control signal generating circuit and a switching circuit. The conversion-sensing circuit converts the first signal into a second signal, and senses at least a voltage waveform change of the second signal to generate a time interval. The control signal generating circuit is electrically connected with the conversion-sensing circuit and outputs a control signal according to the time interval. The switching circuit is electrically connected with the power generation apparatus and the control signal generating circuit, and has a plurality switching elements. The switching circuit receives the first signal and conducts one of the switching elements according to the control signal so as to convert the first signal and output an output signal.